Plywood has been used on the interior wall surfaces of the elevator car for a long time. Plywood is cost efficient and endures wear which makes it a suitable material to be used on the interior wall surfaces of an elevator car.
The appearance of plywood is, however, not very appealing restricting the use of plywood as such in modern elevator cars. The appearance of plywood can be improved by painting or by coating plywood with some other material having a more appealing appearance.
The requirements for flame retardation of building materials are also constantly increasing. Plywood is a flammable material and this fact might cause restrictions in the use of plywood in elevator cars. It is, however, possible to treat plywood so that the fire characteristics of plywood are improved. It is possible to impregnate the plywood with fire retardant solutions and to use suitable glues to attach the veneers in the plywood in order to improve the fire characteristics of plywood. Some manufactures provide commercial plywood which has improved fire characteristics. It is naturally easier to achieve better fire characteristics with thick plywood compared to thin plywood.
A coating on the plywood might on the other hand degrade the fire characteristics of the plywood. This is due to the fact that flashover might occur in the coating during fire testing which will degrade the fire characteristics of the plywood. Also the attachment of the coating to the plywood might cause problems in fire testing. The attachment must withstand heat developed during fire to a certain degree.
The fire classes of building material are defined in European stand-and EN 13501-1. The standard defines seven main fire classes i.e. A1, A2, B, C, D, E and F. The additional classes relating to the smoke production properties of the product are s1, s2, s3. The additional classes relating to the formation of flaming droplets or parts of the product are dO, dI, d2. European standard EN 13501-1 also defines the test methods to be used in the different fire classes. A product to be classified in the fire class B must be tested with the SBI-test (Single Burning Item test) in a small room according to European standard EN 13823 and with the inflammability test with a small flame according to European standard EN ISO 11925-2. The results of these tests determine whether the product can be rated in fire class B or not. An internet site Arborite: “HPL Technical Information”, 31 Jan. 2013, XP05076678, Retrieved from the Internet: URL: http://www.arborite.com/us/HPL-Tehcnical-Information comprises a technical guide relating to high pressure laminates (HPL) provided by the company Ar-borite. The section “Arborite fire rated laminates” describes different properties of the Arborite fire rated laminates. The section “Arborite fire rated laminates” states that Arborite high pressure laminate with fire rated properties are suitable for applications where fire retardant properties are required by building codes i.e. elevator cars, stairwalls, public areas, and hospitals. The section “Substrates” states that good quality particleboard and medium or high density fiberboards are satisfactory for use as substrates since they supply the degree of rigidity needed to support the laminate and offer a suitable face for bonding. The section “Substrates” states further that plywood may be used in some applications, but its dimensional movement is significantly less than high decorative laminate. This may result in potential panel warpage, stress cracking, and open seams. The section “Adhesive selector” states that resocinol resin adhesives may be used for bonding decorative laminate to particleboard when heat resistance is required. The section “Laminating principles” states that architectural applications usually require decorative laminate to be bonded to a substrate. Laminating decorative laminate to substrate material should be done according to the proven principles of fabrication. All components should have properties suitable for the end use of the finished product.